Wiktionary
trim up
vb. (context British English) To put up trimmings, especially at Christmas.
Usage examples of "trim up".
My axe was sharp and I'd split enough rails for fences back in Tennessee to know how to trim up a young tree.
I had all those trees to trim up for the new work on the town hall.
Might as well get the nails done, and trim up the only long-haired features the dog possessed—.
The months have twenty eight days, excepting Fallow, which has twenty nine, There is also the Day of the Turn, which serves as an intercalary unit to trim up the irregularity of the year.